The present invention relates to a spray method and a spray system.
Spray equipment comprising a rotary atomizer in the form of a so-called bell to atomize and spray coating liquids onto an object to be coated are known from the U.S. Pats. No. 4,275,838 and 4,505,430; German patent documents 30 00 002 A1 and 35 09 874 A1. They disclose applying a high electrical potential, which may be positive or negative, to the rotary atomizers and/or to the spray coating liquid. Typically the high voltage is in the range of 4 kV to 140 kV. A high-voltage spray system fitted with an irrotational spray nozzle is known form U.S. Pat. No. 3,731,145.
Rotary atomizing elements conventionally assume a bell shape or a disk form and may rotate at speeds up to 60,000 rpm.
The coating liquid may contain solvents or it may be a water-dilutable liquid, in particular paint, colored or clear lacquers/enamels.
The various kinds of coating liquids exhibit different viscosities and different drying rates. The liquid particles in the spray jet assume different shapes, sizes and flight properties on their way from the liquid atomizer to the object to be coated.
The high voltage generates an electric field between the spray system and an electrically conducting, grounded object to be coated. In this manner spray-jet scattering losses are reduced and higher coating rates and better coating qualities are attained. The adhesion of the liquid particles to the object to be coated depend on the kind of coating liquid and the electrostatic field.